1. Technical Field of the Invention
The present invention relates to electrooptical device substrates, electrooptical devices, methods for fabricating the electrooptical device substrates and the electrooptical devices, and methods for tuning the colors of color filters, and more particularly, the present invention relates to a structure of a color filter suitable for a transflective electrooptical device.
2. Description of the Related Art
Hitherto, in known transflective liquid crystal display panels, both a reflective display using external light and a transmissive display using illuminating light such as backlight are made visible. All transflective liquid crystal display panels have a reflective layer therein for reflecting external light and have a structure in which illuminating light such as light from a backlight passes through the reflective layer. Some reflective layers of this type have a pattern in which one aperture (one slit), having a predetermined ratio, is provided at each pixel of the liquid crystal display panel.
FIG. 11 is a schematic sectional view illustrating the schematic structure of a known transflective liquid crystal display panel 100. The liquid crystal display panel 100 has a structure in which a substrate 101 and a substrate 102 are bonded to each other with sealing adhesive 103 and liquid crystal 104 is injected between the substrates 101 and 102.
The substrate 101 has a reflective layer 111, having one aperture 111a at each pixel, formed on the inner surface thereof, and the reflective layer 111 has a color filter 112, having coloring layers 112r, 112g, and 112b and an overcoat film 112p, formed thereon. The overcoat film 112p on the color filter 112 has transparent electrodes 113 formed on the surface thereof.
On the other hand, the substrate 102 has transparent electrodes 121 formed on the inner surface thereof so as to be orthogonal with the transparent electrodes 113 on the substrate 101 which faces the substrate 102. The transparent electrodes 113 above the substrate 101 and transparent electrodes 121 above the substrate 102 have an alignment film and a hard transparent film formed thereon, as required.
Also, the substrate 102 has a retardation film (¼-wave film) 105 and a polarizer 106 sequentially disposed on the outer surface thereof, and the substrate 101 has a retardation film (¼-wave film) 107 and a polarizer 108 sequentially disposed on the outer surface thereof.
When the liquid crystal display panel 100 having the structure as described above is installed in an electronic apparatus such a portable phone or a portable information terminal, the electronic apparatus has a backlight 109 behind the liquid crystal display panel 100. In the liquid crystal display panel 100, during the daytime or in a well-lit place, e.g., in a building, the reflective display is visible since external light is reflected off the reflective layer 111 after passing through the liquid crystal 104, again-passes through the liquid crystal 104, and is emitted from the liquid crystal display panel 100 along a reflecting path R. On the other hand, at night-time or in a dark area, e.g., in the open air, by illuminating the backlight 109, the transmissive display is visible since, after passing through the apertures 111a, a part of the illuminating light from the backlight 109 passes through the liquid crystal display panel 100 and is then emitted from the liquid crystal panel 100 along a transmitting path T.
However, when the color of the liquid crystal display is to be tuned in the foregoing known liquid crystal panel, it is required to prepare photosensitive agents in which the amounts of colorants such as pigments are finely adjusted in order to achieve the desired display color, thereby increasing the material cost and requiring a lot of work for preparing the photosensitive agents. In particular, in the foregoing transflective liquid crystal display panel, since the colors of the transmissive display and the reflective display are different from each other, optimizing the colors of the transmissive display and the reflective display at the same time is impossible. Accordingly, the display colors are set in a moderately compromised manner, thereby giving rise to problems in that improving the display quality of the liquid crystal display panel is difficult and that the foregoing tuning work of the color becomes troublesome burden when the liquid crystal display panel is fabricated.
Also, since light traveling along the transmitting path T passes through the color filter 112 only once while light traveling along the reflecting path R passes through the color filter 112 twice, that is, in both directions, the chroma of the transmissive display is inferior to that of the reflective display. More particularly, since the brightness of the reflective display generally tends to be insufficient, it is necessary to set the color filter 112 so as to have a high light transmission in order to maintain the brightness thereof; however, this arrangement causes the transmissive display to have an insufficient chroma. Moreover, as described above, the number of times the light passes through the color filter in the reflective display is different from that in the transmissive display, and thus the perceived color of the reflective display is dramatically different from that of transmissive display, thereby detracting from the appearance.
Accordingly, the present invention is made so as to solve the foregoing problems. An object of the present invention is to provide a method and a structure in which the color of the color filter can be easily and finely tuned at low cost. Another object of the present invention is to provide an electrooptical device substrate and a transflective electrooptical device which can maintain sufficient brightness of the reflective display and sufficient chroma of the transmissive display at the same time when a display device capable of performing reflective display and transmissive display at the same time is used. Still another object of the present invention is to achieve a display technology which can reduce the difference in the perceived color between the reflective display and the transmissive display.